Wave energy presents a promising path for renewable electricity, yet commercial adoption remains limited due to high capital costs of wave energy converters (WECs). This study investigates the structural and economic feasibility of using reinforced concrete instead of steel for the hull of the Inertial Sea Wave Energy Converter (ISWEC). A concrete-based hull is proposed and evaluated using linear and nonlinear Finite Element Analysis (FEA), with environmental loads assessed via Computational Fluid Dynamics (CFD). Key performance indicators such as cracking, reinforcement behavior, and serviceability were analysed. Cost analysis indicates potential savings in capital expenditure and lifecycle maintenance. Results support the viability of concrete as an alternative material in offshore WEC structures, paving the way for more sustainable and cost-effective wave energy systems.